Method for controlling line printers comprising a revolving type band and a print hammer bank

Abstract

Method for controlling line printers comprising a revolving type band (400) and a print hammer bank for precalculating the firing times of the print hammers. The type band generally comprises equidistantly spaced scannable time marks (402) and a reference mark (501). The character spacing on the type band is subject to a coarse raster pitch ΔT which is derived from the time mark pitch. The time mark positions are associated with coarse raster positions. The arrangement of the print hammers is subject to a coarse raster pitch ΔT and a fine raster pitch ΔT. Coarse and fine raster values are defined as time values. The hammers are sorted according to the fine raster values and their firing times are calculated by means of a special algorithm according to the order resulting from the sort step. The calculated values are entered in a first table (600) (comprising a field for each coarse raster value) and in a second table (700) (in which the fine raster values associated with the coarse raster value are entered). The printer control method permits different character spacings on the type band and variable print hammer pitches, compensating for flight time variations of the hammers, left- and right-shifting characters and dot raster printing (even with different greytones).

I claim: 
     
       1. Method for controlling line printers comprising a revolving type carrier which is moved past a row of print elements arranged in a bank and associated with the print positions of a print line, for precalculating the actuation times Tf of the print elements for printing particular characters at particular print positions of a record carrier at said print line,   using a type carrier with equidistant1y spaced scannable time marks and a reference mark, and   characterized in   that the spacing of the characters on the type carrier (400) relative to the reference mark (501) equals a coarse time raster value (ΔT) or an integral multiple thereof,   that the coarse time raster value is derived from the time mark pitch, with the time marks (402) having specific coarse time raster values,   that the pitch of the print elements in the bank differ and the spacing of a print position from a reference print posiiton (H1) equals a coarse time raster value (ΔT) or a multiple thereof and an additional fine time raster value (.sup.Δ t) or a multiple thereof,   the coarse and fine time raster values being defined as coarse and fine time raster values relative to the number of revolutions of the type carrier (400),   that the fine time raster values of the print elements are sorted according to the fine time raster values of their spacing from the reference print position and   their actutation times (Tf) are calculated in the order of the print elements resulting from that sort step,   and that the actuation time of a print element at the nth print position Hn (n=1, 2, 3, 4, . . . ) for printing the pth character Cp (p=1, 2, 3, 4, . . . ) on the type carrier with the characters being consecutively numbered relative to othe reference mark (501) and the print positions being consecutively numbered relative to the reference print position (H1)   is calculated according to the relation   Tf=TCp-THn     for a positive difference value TCF-THn   Tf=TC Band+(TCp-THn)       for a negative difference value TCp-THn     which is subtracted from TC Band,   where TC band is the time required for one revolution of the band and TCp is the time that passes as the pth character moves from its respective momentary position to the reference print position (H1), and   where THn is the time that passes as the type band moves from the nth print position Hn to the reference print position (H1),   and where T Home is the time that passes as the reference mark (501) moves from its respective mommetary position to the reference print position (H1),   and that a first table FTABC (600) and a second table FTABF (700) are generated,   the first table (600) comprising a field for each possible coarse raster time value in an ascending order,   and the second table (700) comprising a row field (700 ΔT5) associated with each coarse raster time value of the first table (600) and consisting of several subfields (700 .sup.Δ T5-1, 700 .sup.Δ T5-2),   and that after calculation of the actuation time of a print element, an entry for the coarse time raster value of the calculated actuation time is made in the associated field of the table (600) for the print operation to be performed later on,   and for the fine time raster value of the calculated actuation time an entry on the print position number and the fine time raster value for the print operation to be performed later on is made in the next free subfield of the row field associated with the coarse time raster,   and that for printing a line, the fields of the first table (600) are addressed in the ascending order of the coarse time raster values,   and that in the event of a coarse time raster table field entry for a print operation to be performed a branch is taken to the row field of the second table (700) associated with that coarse time value, printing the print positions defined therein in the order of the fine time raster values at a time obtained by adding the coarse time raster value and the respective fine time raster value.   
     
     
       2. Method according to claim 1, characterized in that changing the coarse time raster values (TCi) causes the characters to be printed left- or right-shifted from their original print position. 
     
     
       3. Method according to claim 2, characterized in that changing the fine time raster values prior to sorting the print elements according to the fine time raster values causes flight time variations of the print elements to be compensated for. 
     
     
       4. Method according to claim 3, characterized in that by using a type carrier with a plurality of dots and engraved characters as a type band, a dot raster/engraved characterer print output is obtained. 
     
     
       5. Method according to claim 3, characterized in that by using a type carrier with a plurality of dots as a type band, a dot raster print output is obtained. 
     
     
       6. Method according to claim 5, characterized by overlapping and/or non-overlapping dot printing. 
     
     
       7. Arrangement for implementing the method according to claim 6 for gapless dot printing, characterized in that the type band (20) comprises two tracks (20-10, 20-20) of dot characters, the first track of which in a first print cycle serves to print a dot row with gaps caused by the mutual spacing of the print elements (131, 132, 133), and the second track of which after advance of the record carrier by a value corresponding to the track spacing (P) serves to fill the dot gaps, the impact faces of the print elements (131, 132, 133) comprising two impact regions (131-2; 131-11) for the first and the second track, which are staggered relative to each other. 
     
     
       8. Arrangement for implementing the method according to claim 7 for gapless dot printing, characterized in that for gap-free dot raster printing the print elements are designed as print hammers (131, 132, 133) such that adjacent impact faces have an oblique stepped or similarly shaped spacer gap (140-2, 140-1) extending substantially obliquely to the line direction, and that an assumed plane extending transversely to the line direction and perpendicularly to the impact face of a print hammer intersects the impact face of one of the two adjacent print hammers in a partial region of the spacer gaps,   that a first and a second track (20-10, 20-20) of dot characters is provided on the type band (20),   and that a dot line (160) is printed on the record carrier (140) in a first and a second print cycle,   printing in the first print cycle, by means of the first dot character track (20-10) and the lower portion (131-2) of the print hammer impact faces, a dot line (150) having gaps in the region of the spacer gaps between adjacent print hammers,   and, after the record carrier has been advanced transversely to the line direction by an amount (P) corresponding to the spacing of the dot character tracks, filling said gaps with dots by means of the second dot character track and the upper portion of the print hammer impact faces (131-1).   
     
     
       9. Type band for implementing the method according to claim 1, characterized in that broad adjacent characterers on the type band have a greater spacing from one character centerline to another than narrower characters.